Help please

Mrs Phillips needs to create a box to hold all of her math gadgets. It will be from a rectangular piece of stiff cardboard, having dimensions (length 11 inches) (width 10 inches) (height x inches) created by cutting out square corners. With side length x and folding up the sides


(A) Write an equation for the volume of the box in terms of x.


(B) Estimate the value of x to the nearest tenth, that gives greatest volume


(C) Explain what the x and y coordinates at the peak curve represents